Fix for gitsigns background colors and new Telescope defaults

[stonefeld]

GitSign colors were not consistent with the SignColumn without transparent_mode = true option activated.

That has been fixed by making GitSigns colors match each corresponding sign highlight definition.

GitSignsAdd = { link = "GruvboxGreenSign" },    
GitSignsChange = { link = "GruvboxOrangeSign" },
GitSignsDelete = { link = "GruvboxRedSign" },

Also I've changed Telescope's defaults to match a nicer style out of the box.

[Copilot]

Pull Request Overview

This PR fixes visual inconsistencies in the gruvbox theme by adjusting gitsigns colors to match their corresponding sign column highlights and updating Telescope defaults for better out-of-the-box styling.

• Updated GitSigns highlight groups to link to Sign variants for consistent background colors
• Added GitSignsCurrentLineBlame highlight group
• Revised Telescope border and title styling for improved visual appearance

Comments suppressed due to low confidence (1)

lua/gruvbox.lua:488

• The TelescopePrompt highlight group is being removed but there's no replacement defined. This could leave the prompt area without proper styling.

    CmpItemAbbr = { link = "GruvboxFg0" },